The Fabry-Perot interferometer (FPI) has been traditionally used to examine either small spectral ranges or relatively simple spectra. Recently, however, the studies have shown that the FPI can be competitive with the Michelson interferometer over extended spectral ranges. A relatively new FPI is described based on two gratings. In order to measure angular micro-displacement, a novel grating angular displacement transducer using a multiplex Fabry-Perot interference technology has been developed in this paper.